Field of the Invention
The present invention relates to movable body apparatuses, exposure apparatuses, exposure methods, and device manufacturing methods, and more particularly, to a movable body apparatus including a movable body which can move along a plane parallel to a predetermined two-dimensional plane, an exposure apparatus which is equipped with the movable body apparatus and exposes an object with an energy beam, an exposure method performed in the exposure apparatus, and a device manufacturing method using the exposure apparatus or the exposure method.
Description of the Background Art
Conventionally, in a lithography process for manufacturing electron devices (microdevices) such as semiconductor devices (such as integrated circuits) and liquid crystal display devices, exposure apparatuses such as a projection exposure apparatus by a step-and-repeat method (a so-called stepper) and a projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner) are mainly used.
In these types of exposure apparatuses, the position of a wafer stage which moves two-dimensionally, holding a substrate (hereinafter generally referred to as a wafer) such as a wafer or a glass plate on which a pattern is transferred and formed, was measured using a laser interferometer in general. However, requirements for a wafer stage position control performance with higher precision are increasing due to finer patterns that accompany higher integration of semiconductor devices recently, and as a consequence, short-term variation of measurement values due to temperature fluctuation and/or the influence of temperature gradient of the atmosphere on the beam path of the laser interferometer can no longer be ignored.
To improve such an inconvenience, various inventions related to an exposure apparatus that has employed an encoder having a measurement resolution at the same level or better than a laser interferometer as the position measuring device of the wafer stage have been proposed (refer to, e. g., PCT International Publication No. 2007/097379 (the corresponding U.S. Patent Application Publication No. 2008/0088843) and the like). However, in the liquid immersion exposure apparatus disclosed in PCT International Publication No. 2007/097379 and the like, there still were points that should have been improved, such as a threat of the wafer stage (a grating installed on the wafer stage upper surface) being deformed when influenced by heat of vaporization and the like when the liquid evaporates.
To improve such an inconvenience, in, for example, PCT International Publication No. 2008/038752 (the corresponding U.S. Patent Application Publication No. 2008/0094594), as a fifth embodiment, an exposure apparatus is disclosed which is equipped with an encoder system that has a grating arranged on the upper surface of a wafer stage configured by a light transmitting member and measures the displacement of the wafer stage related to the periodic direction of the grating by making a measurement beam from an encoder main body placed below the wafer stage enter the wafer stage and be irradiated on the grating, and by receiving a diffraction light which occurs in the grating. In this apparatus, because the grating is covered with a cover glass, the grating is immune to the heat of vaporization, which makes it possible to measure the position of the wafer stage with high precision.
However, depending on the type of exposure apparatus (for example, in an exposure apparatus which employs a dual stage structure as is disclosed in, U.S. Pat. No. 7,161,659), it becomes necessary to move a wafer stage inside a measurement range (e.g., an exposure position) of an encoder system, after a predetermined processing (e.g., alignment measurement of a wafer) has been performed on a wafer outside the measurable range of the encoder system. Accordingly, development of a system that can measure positional information of a wafer stage in a much wider range with high accuracy was desired.